Adapted from: Ripe by Nigel Slater
Preheat the oven to 350 F. Cut the chocolate into pieces (unless you’ve already got feves or smaller pieces on hand, obviously) and put them into a small heatproof glass bowl. Place the bowl over a small pan of simmering water, with the bottom of the bowl not quite touching the water. Allow the chocolate to melt, stirring occasionally.
Beat the butter and sugar together in a stand mixer until smooth and creamy. Break the eggs into a small bowl and whisk them just enough to break them up. Add the eggs and vanilla to the butter and sugar, beating constantly. Scrape down the bowl if necessary and continue mixing. Add the melted chocolate slowly.
Toast the hazelnuts in a shallow pan until golden and fragrant. Allow them to cool. Grind the nuts coarsely to the texture of chunky gravel, then remove half of them and continue grinding the other half until it resembles fine breadcrumbs. Add the flour, baking powder, and salt and both textures of nuts to the mixture. Mix only until combined.
Place large heaping tablespoons of the mixture on a baking sheet lined with parchment paper. Leave about 1-inch in between each cookie –they don’t spread too terribly much. Bake for 10 minutes after which time the cookies should still feel soft and just a touch gooey in the center. They will firm up completely as they cool. As soon as they’re cool enough to move without breaking, transfer to a wire cooling rack. If kept airtight at room temperature, cookies will be good for at least 3 day